一种新型双端口三电平变换器

A novel dual-port three-level converter

针对传统背靠背三电平变换器成本高、体积大、结构复杂等问题,文中提出一种新型双端口三电平变换器拓扑,通过器件复用方式减少开关器件数量,优化系统结构。首先,详细分析所提新型拓扑的工作原理,给出单相桥臂的6种有效开关状态、电流流通路径及对应双端口输出电平,并对各开关器件的电压应力进行分析。其次,研究并设计一种适用于该新型拓扑的载波层叠脉宽调制策略,加入直流偏移量以避免调制波重合产生的影响。然后,进一步分析该策略在同频与异频工作模式下的调制度范围、相角差约束等关键问题,给出各工作模式下直流偏移量选取原则及两端口调制度约束范围。最后,基于DSP-FPGA-Typhoon HIL 402实验平台对不同工作模式进行验证。实验结果表明,在实现所提新型拓扑双端口电压电流稳定输出的前提下,加入直流偏移量的载波层叠脉宽调制策略使得变换器输出的电能质量良好,谐波含量低。

Aiming to address the problems of high cost,large size and complex structure of the traditional back-to-back three-level converter,this paper proposes a new dual-port three-level converter topology.This new topology reduces the number of switching devices and optimizes the system size through device multiplexing.Firstly,the operating principle of the proposed converter topology is analyzed in detail,outlining the six effective switching states,current flow paths,and corresponding dual-port output levels of the single leg,while also discussing and the voltage stresses of each switching device.Secondly,a level-shifting pulse width modulation for the proposed converter topology is investigated and designed,and the effect of modulating wave overlap is avoided by adding DC offsets.Thirdly,the key problems of the modulation scheme under both the common frequency and different frequency operation modes,such as the modulation regime range and phase angle difference constraints are analyzed.The principles for selecting DC offsets and constraint range of two-port modulation system in each operating mode are introduced.Finally,the different operating modes are verified using the DSP-FPGA-Typhoon HIL 402 experimental platform.The experimental results show that level-shifting pulse width modulation with DC offsets makes the output power quality of the converter better and the harmonic content lower on the premise of achieving stable output of voltage and current for the proposed converter topology.